Training on Mount Sagiri

Morning mist shrouded the depths of Mount Sagiri like a veil.

Moyu had been traveling through the mountain forest with Giyu Tomioka for eight hours. The deeper they went, the thicker the mist grew, until visibility fell below ten meters. But the Six Eyes allowed Moyu to "see" the flow of energy through the fog: the life force of the trees, the faint fluctuations of the earth's veins, and even the distribution of moisture in the air.

"We're here," Giyu said, suddenly stopping.

The outline of a simple wooden cabin emerged from the mist ahead. A clearing in front held a stone water vat and wooden training posts. Most striking of all were the dozen or so fox masks standing at the edge of the clearing, carved with different expressions as they silently watched the visitors.

The cabin door opened.

An old man wearing a red Tengu Mask stepped outside. He was not particularly tall, but he had a mountain's steady composure. Beneath his dark blue haori was a simple training outfit, and a sheathed Nichirin Blade hung at his waist.

"Giyu." The old man's voice was calm as water, with a faint echo through the mask.

"Master." Giyu bowed slightly. "I've brought someone. He survived an encounter with a Demon without a Nichirin Blade."

Sakonji Urokodaki turned his gaze to Moyu. In that instant, Moyu felt as though a tangible gaze had pierced his body, examining every inch of bone and every muscle.

"Unusual eyes," Urokodaki said evenly. "Giyu mentioned them in his letter. But there's... more to you than that."

Moyu felt a slight chill. As expected of the Former Water Hashira, his perception was frighteningly sharp.

"Come closer." Urokodaki beckoned.

Moyu did as instructed, stopping three paces away from the old man. Urokodaki suddenly reached out and pressed a hand to Moyu's forehead, quick as lightning.

There was no hostility, only examination.

Moyu held himself back from activating the Six Eyes' defense mechanism. He felt a gentle but tenacious energy seep in from Urokodaki's palm. It was the energy of a Breathing Style refined through countless trials, and after circulating once through Moyu's meridians, it withdrew.

"Extraordinary recovery, and traces of unknown energy in your body." Urokodaki withdrew his hand, his eyes beneath the mask seeming thoughtful. "Giyu says you want to learn Water Breathing."

"Yes," Moyu answered firmly.

"Why?"

The question seemed simple, but it was the hardest to answer. Moyu fell silent for a moment, gathering his thoughts.

"Because I've seen Demons eat people," he said slowly. "Because I nearly became a victim. Because... I don't want to be powerless again. Power isn't an end in itself, but only with power can I protect the people I should protect and change the things I should change."

His words were half true and half false, but they came from the heart. He really did want to protect those people—the characters who had been left with regrets in the original story.

Urokodaki watched him silently for a long while before saying, "Giyu, you can go back. He stays here."

Giyu nodded and turned away without saying goodbye, disappearing into the mist. That was his style.

"Follow me." Urokodaki walked around the back of the cabin.

Moyu followed and found a larger clearing behind the cabin, filled with training equipment: enormous round stones, wooden posts of varying thicknesses, pools of different depths, and a steep rock wall.

"The foundation of Water Breathing isn't swordsmanship, but breathing." Urokodaki sat down on a flat stone. "Now sit down, close your eyes, and breathe as I instruct you."

Moyu sat cross-legged and closed his eyes as instructed.

"Inhale—four seconds. Hold—seven seconds. Exhale—eight seconds. Repeat."

This was the basic introduction to the Breathing Style. Moyu tried to follow the rhythm, but soon discovered a problem: his breathing was constantly disrupted by the environmental information the Six Eyes collected automatically. The movement of air molecules, the heartbeats of distant birds, even the crawling of insects and ants in the soil—all of it poured into his mind without pause.

"Your mind isn't calm," Urokodaki said. "The first step of a Breathing Style is learning to shut out distracting thoughts and focus on yourself."

"I... have trouble shutting them out." Moyu opened his eyes with a wry smile. "My eyes collect information automatically. I can't turn that off."

"Then don't turn it off." Urokodaki stood. "Try another method. Follow me."

He led Moyu to a pool. It was about a meter deep and clear enough to see the smooth pebbles lining the bottom.

"Get in, sit cross-legged, and let the water reach your chest," Urokodaki instructed.

Moyu removed his outer clothes and stepped into the water. The mountain spring water was piercingly cold in early spring, and he couldn't help shivering.

"Now activate your eyes and observe with all your strength," Urokodaki said. "But don't observe your surroundings. Observe the water."

"Observe the water?"

"Its movement, its temperature, the tiny creatures in it, the way it touches your skin." Urokodaki crouched beside the pool. "Focus all that excess perception of yours on this pool of water. When you can 'hear' the rhythm of my breathing through the water, we'll move on to the next step."

It was a clever method. If the Six Eyes' information overload couldn't be solved, he could direct them to focus on a single object.

Moyu took a deep breath and fixed the Six Eyes' vision on the water around him.

The world changed in an instant.

He saw the vibration frequencies of water molecules, the subtle convection currents formed by differences in water temperature, and the changes in surface tension where the water touched his skin. Going further, he "saw" the ripples of sound transmitted through the water—the vibrations of wind blowing through distant leaves reaching his senses through the water's surface.

But where was the sound of Urokodaki's breathing?

Moyu held his breath and concentrated, sharpening his perception further and further. Water was an excellent conductor, and vibrations within the human body would pass into it through contact. He needed to separate that particular frequency from the countless sources of environmental noise.

Time passed. The sun rose in the east, reached its zenith, and slowly began to descend in the west.

Moyu's lips turned purple from the cold, and his body trembled slightly in the water, but his mind was unusually focused. The Six Eyes were operating beyond their limits, and a faint headache began to set in, but he gritted his teeth and persevered.

Suddenly, he caught it.

Not through his ears, but through the water: faint, regular vibrations coming from the bank where Urokodaki sat. They were the rise and fall of his chest, the tremor of air passing through his throat, the most fundamental rhythm of life.

Inhale—four seconds. Hold—seven seconds. Exhale—eight seconds.

Moyu unconsciously began breathing in time with that rhythm. Something wondrous happened: as his breathing synchronized with Urokodaki's, his body trembled less, the icy sting turned into a cool, comfortable sensation, and even the headache caused by the Six Eyes eased considerably.

"That's enough. Come out." A trace of approval entered Urokodaki's voice. "To reach this point on your first day, your talent really is unusual."

Moyu climbed out of the pool, and Urokodaki handed him a dry cloth and a clean set of training clothes.

"Get changed and eat. We'll do physical training this afternoon."

Lunch was a simple meal of grilled fish and rice balls, but Moyu found it especially delicious. His body had expended too much energy and urgently needed replenishing.

After a short rest following lunch, Urokodaki began the real training.

"Water Breathing requires a strong body as its foundation. Starting today, your daily training will include fifty mountain climbs carrying a stone, four hours of balance training on wooden posts, a thousand swings chopping firewood, and—cutting through a waterfall."

"Cutting through... a waterfall?" Moyu stared at him in astonishment.

Urokodaki pointed to a distant cliff. "There's a small waterfall over there. When you can cut through its flow for an instant with a Wooden Sword, you'll learn the first form."

Moyu looked at the waterfall, which stood about ten meters high. Water cascaded down, throwing up white spray in the pool below. Cut through the flow with a Wooden Sword? Was that really something a human could do?

"Think it's impossible?" Urokodaki seemed to see through his thoughts. "Every Hashira of the Demon Slayer Corps has done the impossible. If you think it's too hard, you can leave."

"No, I'll learn." Moyu clenched his fists.

The first day's training was almost brutal.

For the stone-carrying climbs, Moyu had to hold a twenty-five-kilogram round stone and run from the foot of the mountain to halfway up, then return. On his first attempt, he was panting and his legs were weak after only a third of the way.

"Breathe! Keep the rhythm!" Urokodaki called from nearby. "Use your breathing to drive your body, not brute force!"

Moyu tried to adjust his breathing to the rhythm he had grasped that morning. Gradually, he felt his lungs expand more fully, oxygen being efficiently delivered to his muscles. It was still strenuous, but at least he could keep going.

The balance training on the wooden posts was even harder. Posts of uneven heights were arranged in a formation, and Moyu had to move quickly across them without touching the ground. The Six Eyes' dynamic vision helped him anticipate shifts in his center of gravity, but his coordination couldn't keep up with his thoughts, and he fell off the posts on his third attempt.

"We'll continue tomorrow," Urokodaki said simply.

The most tedious task was chopping firewood. A thousand swings, each one at the same angle and with the same force. Moyu's arms soon ached and swelled, and blisters formed on the hands gripping the axe.

"Rest for the time it takes an incense stick to burn." Urokodaki handed him a bowl of salt water. "Replenish your water and salt."

At dusk, Moyu dragged his nearly broken body to the waterfall. Wooden Sword in hand, he stared at the curtain of water rushing down.

He activated the Six Eyes at full power. He saw the paths of the currents, the gaps between clusters of water molecules, the central point where the impact was strongest, and the relatively weak edges.

He swung!

The Wooden Sword sliced into the current, but was swept aside in an instant, unable to halt it even for a moment.

"Water's strength lies in its endless flow." Urokodaki had appeared behind him at some point. "Your eyes can see its weaknesses, but your body can't keep up with your eyes. Continue."

Once, twice, ten times, fifty times...

By sunset, Moyu could no longer lift his arms. But he had felt some progress: he had gone from being completely unable to resist the water to diverting its flow for an extremely brief moment, even if only for a fraction of a second.

"That's enough. Go back and eat, then continue your breathing training," Urokodaki said.

After dinner, Moyu sat cross-legged in his room and continued practicing the Breathing Style. This time, he no longer needed water as a medium; he could enter that rhythm on his own.

[Ding. Basic Breathing Style proficiency: 15%]

[Host detected independently grasping a breathing rhythm. Reward: Coins ×50]

The system notifications lifted Moyu's spirits. Apparently, he could earn rewards not only by completing missions, but also through independent training.

Deep in the quiet of the night, Moyu lay on his simple bedding, aching all over, yet feeling a strange sense of fulfillment. He could feel his body slowly recovering under the nourishment of the Breathing Style, while the energy converted by the Six Eyes accelerated the process.

Faint footsteps sounded outside the window. Moyu opened his eyes alertly, and the Six Eyes activated automatically—he saw an energy outline that was both familiar and unfamiliar.

Dark red hair, a scar on his forehead, a wooden box on his back...

Tanjiro!

Moyu's heart gave a sudden leap. According to the original timeline, Tanjiro should have arrived on Mount Sagiri around this time!

He rose quietly and pushed open the door. In the moonlight, a boy was kneeling before Urokodaki with his forehead pressed to the ground, apparently pleading for something. The wooden box on his back trembled slightly, and a faint breath came from within.

Nezuko.

Moyu's breath caught. The girl who had endured so much suffering in the original story was inside that wooden box right now.

"Please, save my sister!" Tanjiro's voice was thick with tears. "She turned into a Demon, but she hasn't eaten anyone! She protected me. She still has her humanity!"

Urokodaki remained silent, the expression beneath his mask impossible to read.

Moyu walked over. Tanjiro looked up at the sound, and their eyes met.

Those eyes were clear and determined, and even brimming with tears, they had not lost their light. This was Tanjiro Kamado, the soul of Demon Slayer: Kimetsu no Yaiba.

"Mr. Urokodaki," Moyu said, "he's telling the truth."

Tanjiro and Urokodaki both looked at him.

"I can 'see' it." Moyu pointed to his eyes. "The being in that box... her energy is completely different from an ordinary Demon's. There's no scent of blood, no violent fluctuations. Instead, there's a kind of... obsession with protecting."

That was the truth. In the Six Eyes' vision, the energy coming from the wooden box was unbelievably pure, worlds apart from the Demon he had encountered before.

Urokodaki gave Moyu a long look, then said to Tanjiro, "Get up. Let me see your sister."

Tanjiro hurriedly opened the wooden box. Nezuko was curled up inside, her eyes closed and a bamboo tube held in her mouth, as still as a doll.

Urokodaki reached out and gently touched Nezuko's forehead. After a long while, he withdrew his hand.

"Starting tomorrow, you'll stay here," Urokodaki told Tanjiro. "You'll train with Moyu. As for your sister... I'll observe her. If she hurts anyone, I'll behead her myself."

"Thank you! Thank you!" Tanjiro bowed his head to the ground again.

Moyu stepped forward and held out his hand to Tanjiro. "My name is Moyu. We'll be fellow disciples from now on."

Tanjiro took his hand, tears welling up again. "Tanjiro Kamado. This is my sister, Nezuko. Thank you... thank you for speaking up for us."

"I only told the truth." Moyu smiled.

Moonlight fell on the three figures and on Nezuko as she slept peacefully. The distant sound of the waterfall drifted faintly through the air, like the background sound of this world.

Moyu knew the story had officially begun. And this time, with him here, perhaps some endings really could be changed.

Urokodaki looked at the two boys and suddenly said, "Starting tomorrow, your training will double. Since there are two of you, compete with each other. Whoever masters Total Concentration Breathing and cuts through the waterfall first will be able to take part in the Final Selection sooner."

Tanjiro looked bewildered, clearly not yet knowing what the Final Selection was.

Moyu, however, took a deep breath, fighting spirit igniting in his eyes.

Competition? Just what I wanted.

The Six Eyes shimmered with a faint azure glow in the moonlight, reflecting this world destined to be extraordinary.

[Ding. Key characters contacted: Tanjiro Kamado, Nezuko Kamado. Side mission triggered: protect Nezuko from execution by the Demon Slayer Corps. Reward: granted according to completion.]

(Tanjiro's training completion time was changed later.)